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000
FXUS63 KFGF 152021
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
321 PM CDT WED MAY 15 2013

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 320 PM CDT WED MAY 15 2013

THE MAIN CHALLENGE THIS AFTERNOON WILL BE UPCOMING VERY ACTIVE
WEATHER PATTERN LATER THIS WEEK INTO NEXT WEEK. MODELS ARE IN DECENT
AGREEMENT WITH THE OVERALL PATTERN...WITH SOME TIMING/PLACEMENT
DIFFERENCES WITH EVENTUAL LOCATION OF CLOSED UPPER LOW EARLY NEXT
WEEK.

FOR TONIGHT...EXPECT A DRY NIGHT WITH WEAK HIGH PRESSURE MOVING INTO
SW ONTARIO. TEMPS SHOULD FALL TO AROUND NORMAL FOR MID MAY WITH
LIGHT WINDS.

ON THURSDAY...MOISTURE WILL BEGIN INCREASING IN THE SOUTH WITH PWATS
AROUND AN INCH HERE BY LATE IN THE DAY. CAN/T RULE OUT A FEW SHOWERS
DURING THE AFTERNOON HERE...OTHERWISE IT SHOULD REMAIN DRY FOR MOST
AREAS.

FOR THURSDAY NIGHT...THERE WILL BE A THUNDERSTORM COMPLEX MOVING
CLOSE TO THE FAR SOUTHERN FORECAST AREA OVERNIGHT. FOR OUR
REGION...EXPECT INCREASING CHANCES FOR MAINLY SHOWERS AS PWATS RISE
OVER 1 INCH WITH MID LEVEL WAA/MOIST ADVECTION. NOT EXPECTING MUCH
IN THE WAY OF THUNDER...SO FOR NOW WILL LEAVE ALL PRECIP AS
SHOWERS.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 320 PM CDT WED MAY 15 2013

FOR FRIDAY/FRIDAY NIGHT...THE MOIST ADVECTION CONTINUES AS THE SW
FLOW ALOFT BECOMES MORE ESTABLISHED OVER THE EASTERN SLOPES OF THE
ROCKIES. THIS WILL MEAN MORE CHANCES FOR SHOWERS AND SOME ISOLATED
THUNDER WITH DAYTIME HIGHS HINGING ON JUST HOW MUCH INSOLATION WE
RECEIVE.

ON SATURDAY...DEEP MOISTURE WILL MOVE OVER THE REGION BY
AFTERNOON/EVENING WITH PWATS AROUND OR SLIGHTLY HIGHER THAN 1.50
INCHES. THIS COUPLED WITH FAIRLY HIGH CAPES PROGGED NEAR 3000 J/KG
IN THE SOUTH WITH A STRONG SFC WARM FRONT SHOULD PROVIDE THE FOCUS
FOR THUNDERSTORMS. GIVEN THE HIGH INSTABILITY AND MODEST DEEP
LAYERED SHEAR AROUND 40KT...SEVERE STORMS CAN/T BE RULED OUT AND OUR
FAR SOUTH COULD BE CLOSE TO A POTENTIAL LARGER SEVERE WEATHER EVENT
THAT SHOULD UNFOLD OVER SD. IT WILL ALSO GET MUGGY ON SAT WITH SFC
TDS PROGGED INTO THE MID 60S IN THE SOUTH AND NEAR 60 EVEN INTO THE
NORTHERN VALLEY. THE NAM IS FARTHER NORTH WITH POTENTIAL SEVERE
WEATHER THAN THE GFS...BUT ALL AREAS WILL SEE INCREASING CHANCES FOR
SHOWERS AND STORMS BY AFTERNOON WITH LOCALLY HEAVY RAIN ALSO
POSSIBLE.

FOR SATURDAY NIGHT THROUGH WEDNESDAY...THE 12 UTC GFS/ECMWF 500
HPA HEIGHT PATTERN IN GOOD AGREEMENT. ECMWF WAS MORE PROGRESSIVE
YESTERDAY WITH BROAD OPEN PACIFIC WAVE MOVING INTO AND THROUGH
NORTHERN PLAINS...NOW IT IS SIDING WITH ITS NEIGHBORING MODELS IN
A STACKED LOW SOLUTION SITUATED SOMEWHERE OVER THE NORTHERN PLAINS
MONDAY INTO TUESDAY. THE LATTER HALF OF THE WEEKEND WILL FEATURE
SHARP BOUNDARY OVER THE DAKOTAS WITH PERIODIC BOUTS OF HEALTHILY
NEGATIVE LI/SHOWALTERS LEADING TO A LENGTHY PERIOD OF LIKELY TRW
POPS. THIS REGIME IS CORROBORATED BY PRECIPITABLE WATER VALUES
FROM 1.0 TO 1.5 INCHES AND PERSISTENT ENHANCED MID-LEVEL
CONVERGENCE. RAW MODEL QPF SUGGESTS ANYWHERE FROM 1 TO 4 INCHES OF
RAIN THROUGH TUESDAY NIGHT REGION-WIDE. TEMPERATURES WILL FALL
BELOW NORMAL SUNDAY INTO EARLY NEXT WEEK WITH AFTERNOON HIGHS FROM
THE UPPER 50S TO MID 60S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 320 PM CDT WED MAY 15 2013

HIGH PRESSURE SOUTH OF THE REGION WILL KEEP LIGHT WEST TO NORTHWEST
WINDS IN PLACE THROUGH THE EVENING...FOLLOWED BY LIGHT EASTERLY
QUADRANT WINDS OVERNIGHT AS A WEAK HIGH SETTLES IN TO THE NORTH. VFR
CONDITIONS WITH ONLY HIGH CLOUDS EXPECTED THROUGH THURS
AFTN.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&

$$

SHORT TERM...DK
LONG TERM...WJB/DK
AVIATION...WJB